Disorders of the Diaphragm

Review of Point-of-Care Diaphragmatic Ultrasound in Emergency Medicine: Background, Techniques, Achieving Competency, Research, and Recommendations

ABSTRACT

The diaphragm is the major muscle of inspiration accounting for approximately 70% of the inspired tidal volume. Point-of-care diaphragmatic ultrasound offers the ability to quantitatively assess diaphragmatic function, perform serial evaluations over time, and visualize structures above and below the diaphragm. Although interest in point-of-care ultrasound (POCUS) of the diaphragm is developing in the emergency medicine, assessment of the diaphragm and its function is not recognized as a core application by national organizations or expert guidelines. As a result, it is infrequently performed, and its potential value in research or clinical practice may not be fully appreciated. The purpose of this review is to describe the developmental aspects of the diaphragm as it pertains to POCUS, discuss the POCUS techniques for evaluating diaphragmatic function, address competency acquisition in this POCUS application, summarize relevant research in the ED, and provide a summary of recommendations for further research and clinical utilization of POCUS in diaphragm evaluation.

Body Positions and Physical Activity Levels Modulate the Ratio of Abdominal to Thoracic Breathing and Respiratory Rate in Young Individuals

Background/Objectives: The COVID-19 pandemic highlighted that body positions substantially affected the mortality rate. We hypothesized that body position modulates the contribution of abdominal (AB) and thoracic breathing (TB) to the breathing cycle (BC), as well as respiratory rate (RR). In addition, we hypothesized that physical activity level can increase the contribution of abdominal breathing. Methods: Thus, we used plethysmography respiratory belts to measure changes in abdominal (AB) and thoracic (TB) circumferences, their ratio (AB/TB), and respiratory rate (RR) under resting conditions. Measurements were taken in four body positions-standing (St), sitting (Si), supine (Su), and prone (Pr)-for two groups of young adults (aged 21 ± 2 years) with different physical activity levels (low and high PA). Results: The AB/TB ratios significantly differed between the body positions (Si: 45.5/54.5%, St: 40.5/59.5%, Su: 56.8/43.2%, Pr: 52.2/47.8% (p < 0.001)). AB was significantly the highest in Su and lowest in Si and St (p < 0.001). There was a significant difference in respiratory rate (RR) between the four body positions (p = 0.005). RR in the four body positions was the following: Si: 15.1, St: 15.0, Su: 13.7, and Pr: 14.4. RR was the lowest in Su (13.7), where AB was the highest (56.8%), and RR was the highest in Si (15.1) and St (15.0), where TB was higher compared to Su (p < 0.001). PA significantly affected the various body positions' AB/TB ratio and RR. The high PA group showed a significant difference in the AB/TB ratio between the body positions (p < 0.001). The low PA group showed a significant difference in RR between the body positions (p = 0.025). Conclusions: In young, healthy adults, we found that body position significantly influenced the abdominal/thoracic breathing ratio during the breathing cycle. The supine position showed the highest contribution of abdominal breathing, which correlated with the lowest respiratory rate. Additionally, a higher level of physical activity increased the contribution of abdominal breathing in the Si, Su, and St positions, suggesting a more energy-efficient breathing pattern. These findings suggest the potentials for breathing pattern monitoring and position-based interventions to improve healthcare outcomes and enhance sports performance and recovery.

Diaphragmatic ultrasound: approach, emerging evidence, and future perspectives in non-ICU patients

Diaphragmatic dysfunction is an important contributor to hypercapnic respiratory failure, but its presence is often challenging to determine at the bedside. Diaphragm ultrasound provides an opportunity to evaluate the function of the diaphragm noninvasively by evaluating the following parameters that can help define diaphragmatic dysfunction: diaphragm excursion, diaphragm muscle thickness, and thickening fraction. Its evaluation has the potential to assist with diagnosis of respiratory failure, provide prognosis, and assist with patient monitoring and should be considered as part of an internal medicine physician's and emergency physician's skill set. This article provides an overview on how to perform diaphragm ultrasound, review its pitfalls, and discuss the evidence of its use in patients with neuromuscular disorders and chronic obstructive pulmonary disease. Finally, its potential emerging uses in the perioperative setting and for evaluation of acute heart failure are discussed.

Role of diaphragmatic dysfunction in extubation failure among patients at high risk of reintubation: A prospective cohort study

PURPOSE

This study aims to evaluate the role of diaphragmatic dysfunction in extubation failure among patients at high risk of reintubation.

MATERIAL AND METHODS

This prospective cohort study was carried out at a intensive care unit in China. Adult patients who had been intubated for more than 24 h and ready for extubation were included in the study if they exhibited a high risk of extubation failure. Diaphragm dysfunction was defined as a diaphragmatic thickening fraction <30 % or diaphragmatic excursion <10 mm. The primary outcome was defined as extubation failure, which includes either reintubation or death within the initial 7 days following extubation.

RESULTS

Out of the 113 patients, 27 (23.89 %) experienced extubation failure, with diaphragm dysfunction diagnosed in 63 (55.75 %) individuals. Patients who failed extubation were significantly more likely to have diaphragm dysfunction (85.19 % vs. 46.51 %, p < 0.01). In the Cox-proportional hazards regression analysis, diaphragm dysfunction and the Medical Research Council score were found to be associated with extubation failure. The adjusted hazard ratios were 4.56 [95 % CI: 1.56-13.33] and 0.93 [95 % CI: 0.88-0.99]. Both variables were closely correlated with extubation failure showing statistical significance.

CONCLUSION

Diaphragm dysfunction could contribute to an elevated extubation failure rate.

Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat?

Assessing and treating respiratory muscle dysfunction is crucial for patients with both acute and chronic respiratory failure. Respiratory muscle dysfunction can contribute to the onset of respiratory failure and may also worsen due to interventions aimed at treatment. Evaluating respiratory muscle function is particularly valuable for diagnosing, phenotyping and assessing treatment efficacy in these patients. This review outlines established methods, such as measuring respiratory pressures, and explores novel techniques, including respiratory muscle neurophysiology assessments using electromyography and imaging with ultrasound.Additionally, we review various treatment strategies designed to support and alleviate the burden on overworked respiratory muscles or to enhance their capacity through training interventions. These strategies range from invasive and noninvasive mechanical ventilation approaches to specialised respiratory muscle training programmes. By summarising both established techniques and recent methodological advancements, this review aims to provide a comprehensive overview of the tools available in clinical practice for evaluating and treating respiratory muscle dysfunction. Our goal is to present a clear understanding of the current capabilities and limitations of these diagnostic and therapeutic approaches. Integrating advanced diagnostic methods and innovative treatment strategies should help improve patient management and outcomes. This comprehensive review serves as a resource for clinicians, equipping them with the necessary knowledge to effectively diagnose and treat respiratory muscle dysfunction in both acute and chronic respiratory failure scenarios.

Ultrasound assessment of diaphragmatic dysfunction in non-critically ill patients: relevant indicators and update

Diaphragm dysfunction (DD) can be classified as mild, resulting in diaphragmatic weakness, or severe, resulting in diaphragmatic paralysis. Various factors such as prolonged mechanical ventilation, surgical trauma, and inflammation can cause diaphragmatic injury, leading to negative outcomes for patients, including extended bed rest and increased risk of pulmonary complications. Therefore, it is crucial to protect and monitor diaphragmatic function. Impaired diaphragmatic function directly impacts ventilation, as the diaphragm is the primary muscle involved in inhalation. Even unilateral DD can cause ventilation abnormalities, which in turn lead to impaired gas exchange, this makes weaning from mechanical ventilation challenging and contributes to a higher incidence of ventilator-induced diaphragm dysfunction and prolonged ICU stays. However, there is insufficient research on DD in non-ICU patients, and DD can occur in all phases of the perioperative period. Furthermore, the current literature lacks standardized ultrasound indicators and diagnostic criteria for assessing diaphragmatic dysfunction. As a result, the full potential of diaphragmatic ultrasound parameters in quickly and accurately assessing diaphragmatic function and guiding diagnostic and therapeutic decisions has not been realized.

Ultrasonographic changes and impact factors of diaphragmatic function in patients with obstructive sleep apnea-hypopnea syndrome

PURPOSE

Diaphragmatic impairment has been reported in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients. However, the risk factors of diaphragmatic dysfunction are unclear. This study was conducted to evaluate the diaphragmatic function and to investigate impact factors of ultrasonographic changes of the diaphragm in OSAHS patients.

METHODS

This cross-sectional study recruited 150 snoring patients. All patients were divided into the control group (AHI < 5/h, n = 20), the mild-to-moderate OSAHS group (5/h ≤ AHI ≤ 30/h, n = 61), and the severe OSAHS group (AHI > 30/h, n = 69). Diaphragmatic thickness at function residual capacity (TFRC) and total lung capacity (TTLC) were measured by two-dimensional ultrasound, and the diaphragmatic excursion during tidal and deep breath was measured by M-mode ultrasound. The diaphragmatic thickening fraction (TF) was calculated. Spearman analysis and multiple linear stepwise regression analysis were conducted to analyze the impact factors of diaphragmatic function.

RESULTS

TFRC in the control group, mild-to-moderate OSAHS group, and severe OSAHS group was 1.23 (1.10, 1.39) mm, 1.60 (1.43, 1.85) mm, and 1.90 (1.70, 2.25) mm; TTLC was 2.75 (2.53, 2.93) mm, 3.25 (2.90, 3.55) mm, and 3.60 (3.33, 3.90) mm, and TF was 119.23% (102.94, 155.97), 96.55% (74.34, 119.11), and 85.29% (60.68,101.22). There were across-group significant differences in TFRC, TTLC, and TF (P < 0.05). The oxygen desaturation index was the influencing factor of TFRC, TTLC, and TF (P < 0.05).

CONCLUSION

The diaphragm is thickened and diaphragmatic contractility is decreased in OSAHS patients. Nocturnal intermittent hypoxia is a risk factor for diaphragmatic hypertrophy and impaired diaphragmatic contractility.

Diaphragmatic morphological post-mortem findings in critically ill COVID-19 patients: an observational study

Our study investigates the post-mortem findings of the diaphragm's muscular structural changes in mechanically ventilated COVID-19 patients. Diaphragm samples of the right side from 42 COVID-19 critically ill patients were analyzed and correlated with the type and length of mechanical ventilation (MV), ventilatory parameters, prone positioning, and use of sedative drugs. The mean number of fibers was 550±626. The cross-sectional area was 4120±3280 μm2, while the muscular fraction was 0.607±0.126. The overall population was clustered into two distinct populations (clusters 1 and 2). Cluster 1 showed a lower percentage of slow myosin fiber and higher fast fiber content than cluster 2, 68% versus 82%, p<0.00001, and 29.8% versus 18.8%, p=0.00045 respectively. The median duration of MV was 180 (41-346) hours. In cluster 1, a relationship between assisted ventilation and fast myosin fiber percentage (R2=-0.355, p=0.014) was found. In cluster 2, fast fiber content increased with increasing the length of the controlled MV (R2=0.446, p=0.006). A high grade of fibrosis was reported. Cluster 1 was characterized by fibers' atrophy and cluster 2 by hypertrophy, supposing different effects of ventilation on the diaphragm but without excluding a possible direct viral effect on diaphragmatic fibers.

Lung, Pleura, and Diaphragm Point-of-Care Ultrasound

Thoracic Ultrasonography involves the ultrasonographic examination of the lungs, pleura, and diaphragm. This provides a plethora of clinical information during the point of care assessment of patients. The air filled lungs create consistent artifacts and careful examination and understanding of these artefactual signs can provide useful information on underlying clinicopathologic states. This review aims to provide a review of the ultrasound signs and features that can be seen in horacic ultrasonography and summarize the clinical evidence to support its use.

Diaphragm Ultrasonography: Reference Values and Influencing Factors for Thickness, Thickening Fraction, and Excursion in the Seated Position

INTRODUCTION

Measurements of diaphragm function by ultrasonography are affected by body position, but reference values in the seated position have not been established for an Asian population. This study aimed to determine reference values for diaphragm thickness, thickening fraction, and dome excursion by ultrasonography and to investigate the effects of sex, height, and body mass index.

METHODS

Diaphragm ultrasonography was performed on 109 seated Japanese volunteers with normal respiratory function who were enrolled between March 2022 and January 2023. Thickness, thickening fraction, and excursion were measured. Reference values and the measurement success rate were calculated. Multivariate analysis adjusted for sex, height, and body mass index was performed.

RESULTS

The measurement success rate was better for thickness than for excursion. The mean (lower limit of normal) values on the right/left sides were as follows. During quiet breathing, thickness at end expiration(mm) was 1.7 (0.9)/1.6 (0.80), thickening fraction(%) was 50 (0.0)/52 (0.0), and excursion(cm) was 1.7 (0.5)/1.9 (0.5). During deep breathing, the thickening fraction was 111 (24)/107 (22), and the excursion was 4.4 (1.7)/4.1 (2.0). In multivariate analysis, body mass index was positively associated with thickness but not with the thickening fraction.

CONCLUSION

The reference values in this study were smaller than those in previous reports from Europe. Considering that thickness is influenced by body mass index, using Western reference values in Asia, where the average body mass index is lower, might not be appropriate. The thickening fraction in deep breathing is unaffected by other items and can be used more universally.

Perioperative Diaphragm Dysfunction

Diaphragm Dysfunction (DD) is a respiratory disorder with multiple causes. Although both unilateral and bilateral DD could ultimately lead to respiratory failure, the former is more common. Increasing research has recently delved into perioperative diaphragm protection. It has been established that DD promotes atelectasis development by affecting lung and chest wall mechanics. Diaphragm function must be specifically assessed for clinicians to optimally select an anesthetic approach, prepare for adequate monitoring, and implement the perioperative plan. Recent technological advancements, including dynamic MRI, ultrasound, and esophageal manometry, have critically aided disease diagnosis and management. In this context, it is noteworthy that therapeutic approaches for DD vary depending on its etiology and include various interventions, either noninvasive or invasive, aimed at promoting diaphragm recruitment. This review aims to unravel alternative anesthetic and operative strategies that minimize postoperative dysfunction by elucidating the identification of patients at a higher risk of DD and procedures that could cause postoperative DD, facilitating the recognition and avoidance of anesthetic and surgical interventions likely to impair diaphragmatic function.

Assessment of the Diaphragm Thickness Decrease in Critically Ill COVID-19 Patients: Could Computed Tomography Be of Aid Regarding Diaphragm Muscle Mass?

INTRODUCTION

The diaphragm has a significant clinical value on respiratory performance. There is little literature on the use of thorax computed tomography for the purpose of identifying alterations in diaphragm thickness in critically ill patients diagnosed with COVID-19. The present study aims to investigate dynamic changes in muscle thickness and its association with clinical outcomes.

METHODS

A single-center retrospective observational study was conducted in a tertiary intensive care unit (ICU). The study comprised adult patients with severe COVID-19 who were admitted to the ICU and underwent two thorax CT scans. We measured diaphragmatic thickness at the level of the celiac truncus.

RESULTS

The average reduction in thickness of the dynamic diaphragm was found to be -0.58 mm for the right diaphragm and -0.54 mm for the left diaphragm. The diaphragm thickness exhibited a substantial decrease on both the right and left sides in both CT scans (p=0.02). A negative correlation coefficient was observed for both the right and left diaphragm. The criterion indicating a poor prognosis for the right diaphragm was a value greater than -0.175, whereas it was more significant for the left diaphragm than -0.435. The cut-off values indicated a high risk of prolonged mechanical ventilation and an increased risk of ICU mortality.

CONCLUSION

 CT diaphragm evaluation in mechanically ventilated COVID-19 patients has the possibility of becoming a reliable tool for predicting muscle modifications.

Effects of inspiratory muscle training on exertional breathlessness in patients with unilateral diaphragm dysfunction: a randomised trial

Background

Unilateral diaphragm dysfunction (UDD) is an underdiagnosed cause of dyspnoea. Inspiratory muscle training (IMT) is the only conservative treatment for UDD, but the mechanisms of improvement are unknown. We characterised the effects of IMT on dyspnoea, exercise tolerance and respiratory muscle function in people with UDD.

Methods

15 people with UDD (73% male, 61±8 years) were randomised to 6 months of IMT (50% maximal inspiratory mouth pressure (PI,max), n=10) or sham training (10% PI,max, n=5) (30 breaths twice per day). UDD was confirmed by phrenic nerve stimulation and persisted throughout the training period. Symptoms were assessed by the transitional dyspnoea index (TDI) and exercise tolerance by constant-load cycle tests performed pre- and post-training. Oesophageal (Pes) and gastric (Pga) pressures were measured with a dual-balloon catheter. Electromyography (EMG) and oxygenation (near-infrared spectroscopy) of respiratory muscles were assessed continuously during exercise.

Results

The IMT group (from 45±6 to 62±23% PI,max) and sham group (no progression) completed 92 and 86% of prescribed sessions, respectively. PI,max, TDI scores and cycle endurance time improved significantly more after IMT versus sham (mean between-group differences: 28 (95% CI 13-28) cmH2O, 3.0 (95% CI 0.9-5.1) points and 6.0 (95% CI 0.4-11.5) min, respectively). During exercise at iso-time, Pes, Pga and EMG of the scalene muscles were reduced and the oxygen saturation indices of the scalene and abdominal muscles were higher post- versus pre-training only in the IMT group (all p<0.05).

Conclusion

The effects of IMT on dyspnoea and exercise tolerance in UDD were not mediated by an improvement in isolated diaphragm function, but may reflect improvements in strength, coordination and/or oxygenation of the extra-diaphragmatic respiratory muscles.

Validation of Point-of-Care ultrasound in the diagnosis of a diaphragmatic hernia

Point-of-care ultrasound (POCUS) is a sensitive, specific tool for early diagnosis of diaphragm pathology in critically ill patients. We report the case of a patient with a history of iatrogenic diaphragmatic hernia who was admitted to the Resuscitation Unit after an emergency exploratory laparotomy. As the diagnosis of diaphragmatic hernia had already been confirmed, we determined the POCUS features that establish the diagnosis of diaphragmatic hernia: (1) normal bilateral diaphragmatic shortening fraction; (2) decreased diaphragmatic excursion; and (3) cephalic position of the diaphragmatic dome (4) greater in supine than in sitting position. We also outline a systematic ultrasound examination of the diaphragm and a POCUS-based differential classification of diaphragmatic dysfunction based on the functional integrity of the peripheral muscle and central diaphragmatic tendon in critically ill patients.

Proof of concept of an accelerometer as a trigger for unilateral diaphragmatic pacing: a porcine model

BACKGROUND

Unilateral diaphragmatic paralysis in patients with univentricular heart is a known complication after pediatric cardiac surgery. Because diaphragmatic excursion has a significant influence on perfusion of the pulmonary arteries and hemodynamics in these patients, unilateral loss of function leads to multiple complications. The current treatment of choice, diaphragmatic plication, does not lead to a full return of function. A unilateral diaphragmatic pacemaker has shown potential as a new treatment option. In this study, we investigated an accelerometer as a trigger for a unilateral diaphragm pacemaker (closed-loop system).

METHODS

Seven pigs (mean weight 20.7 ± 2.25 kg) each were implanted with a customized accelerometer on the right diaphragmatic dome. Accelerometer recordings (mV) of the diaphragmatic excursion of the right diaphragm were compared with findings using established methods (fluoroscopy [mm]; ultrasound, M-mode [cm]). For detection of the amplitude of diaphragmatic excursions, the diaphragm was stimulated with increasing amperage by a cuff electrode implanted around the right phrenic nerve.

RESULTS

Results with the different techniques for measuring diaphragmatic excursions showed correlations between accelerometer and fluoroscopy values (correlation coefficient 0.800, P < 0.001), accelerometer and ultrasound values (0.883, P < 0.001), and fluoroscopy and ultrasound values (0.816, P < 0.001).

CONCLUSION

The accelerometer is a valid method for detecting diaphragmatic excursion and can be used as a trigger for a unilateral diaphragmatic pacemaker.

Diaphragm and Phrenic Nerve Ultrasound in COVID-19 Patients and Beyond: Imaging Technique, Findings, and Clinical Applications

The diaphragm, the principle muscle of inspiration, is an under-recognized contributor to respiratory disease. Dysfunction of the diaphragm can occur secondary to lung disease, prolonged ventilation, phrenic nerve injury, neuromuscular disease, and central nervous system pathology. In light of the global pandemic of coronavirus disease 2019 (COVID-19), there has been growing interest in the utility of ultrasound for evaluation of respiratory symptoms including lung and diaphragm sonography. Diaphragm ultrasound can be utilized to diagnose diaphragm dysfunction, assess severity of dysfunction, and monitor disease progression. This article reviews diaphragm and phrenic nerve ultrasound and describes clinical applications in the context of COVID-19.

Musculoskeletal involvement of COVID-19: review of imaging

The global pandemic of coronavirus disease 2019 (COVID-19) has revealed a surprising number of extra-pulmonary manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. While myalgia is a common clinical feature of COVID-19, other musculoskeletal manifestations of COVID-19 were infrequently described early during the pandemic. There have been emerging reports, however, of an array of neuromuscular and rheumatologic complications related to COVID-19 infection and disease course including myositis, neuropathy, arthropathy, and soft tissue abnormalities. Multimodality imaging supports diagnosis and evaluation of musculoskeletal disorders in COVID-19 patients. This article aims to provide a first comprehensive summary of musculoskeletal manifestations of COVID-19 with review of imaging.

Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction

Diaphragm muscle dysfunction is increasingly recognized as an important element of several diseases including neuromuscular disease, chronic obstructive pulmonary disease and diaphragm dysfunction in critically ill patients. Functional evaluation of the diaphragm is challenging. Use of volitional maneuvers to test the diaphragm can be limited by patient effort. Non-volitional tests such as those using neuromuscular stimulation are technically complex, since the muscle itself is relatively inaccessible. As such, there is a growing interest in using imaging techniques to characterize diaphragm muscle dysfunction. Selecting the appropriate imaging technique for a given clinical scenario is a critical step in the evaluation of patients suspected of having diaphragm dysfunction. In this review, we aim to present a detailed analysis of evidence for the use of ultrasound and non-ultrasound imaging techniques in the assessment of diaphragm dysfunction. We highlight the utility of the qualitative information gathered by ultrasound imaging as a means to assess integrity, excursion, thickness, and thickening of the diaphragm. In contrast, quantitative ultrasound analysis of the diaphragm is marred by inherent limitations of this technique, and we provide a detailed examination of these limitations. We evaluate non-ultrasound imaging modalities that apply static techniques (chest radiograph, computerized tomography and magnetic resonance imaging), used to assess muscle position, shape and dimension. We also evaluate non-ultrasound imaging modalities that apply dynamic imaging (fluoroscopy and dynamic magnetic resonance imaging) to assess diaphragm motion. Finally, we critically review the application of each of these techniques in the clinical setting when diaphragm dysfunction is suspected.

Physiological changes and compensatory mechanisms by the action of respiratory muscles in a porcine model of phrenic nerve injury

Phrenic nerve damage may occur as a complication of specific surgical procedures, prolonged mechanical ventilation, or physical trauma. The consequent diaphragmatic paralysis or dysfunction can lead to major complications. The purpose of this study was to elucidate the role of the nondiaphragmatic respiratory muscles during partial or complete diaphragm paralysis induced by unilateral and bilateral phrenic nerve damage at different levels of ventilatory pressure support in an animal model. Ten pigs were instrumented, the phrenic nerve was exposed from the neck, and spontaneous respiration was preserved at three levels of pressure support, namely, high, low, and null, at baseline condition, after left phrenic nerve damage, and after bilateral phrenic nerve damage. Breathing pattern, thoracoabdominal volumes and asynchrony, and pressures were measured at each condition. Physiological breathing was predominantly diaphragmatic and homogeneously distributed between right and left sides. After unilateral damage, the paralyzed hemidiaphragm was passively dragged by the ipsilateral rib cage muscles and the contralateral hemidiaphragm. After bilateral damage, the drive to and the work of breathing of rib cage and abdominal muscles increased, to compensate for diaphragmatic paralysis, ensuing paradoxical thoracoabdominal breathing. Increasing level of pressure support ventilation replaces this muscle group compensation. When the diaphragm is paralyzed (unilaterally and/or bilaterally), there is a coordinated reorganization of nondiaphragmatic respiratory muscles as compensation that might be obscured by high level of pressure support ventilation. Noninvasive thoracoabdominal volume and asynchrony assessment could be useful in phrenic nerve-injured patients to estimate the extent and type of inspiratory muscle dysfunction.NEW & NOTEWORTHY This was the first (to our knowledge) implanted porcine model of phrenic nerve injury with a detailed multidimensional analysis of different degrees of diaphragmatic paralysis (unilateral and bilateral). Noninvasive thoracoabdominal volume and asynchrony assessment was shown to be useful in estimating the extent of diaphragmatic dysfunction and the consequent coordinated reorganization of nondiaphragmatic respiratory muscles. High level of pressure support ventilation was proved to obscure the interaction and compensation of respiratory muscles to deal with phrenic nerve injury.

Unilateral diaphragmatic paralysis: inspiratory muscles, breathlessness and exercise capacity

Background

Patients with unilateral diaphragmatic paralysis (UDP) may present with dyspnoea without specific cause and limited ability to exercise. We aimed to investigate the diaphragm contraction mechanisms and nondiaphragmatic inspiratory muscle activation during exercise in patients with UDP, compared with healthy individuals.

Methods

Pulmonary function, as well as volitional and nonvolitional inspiratory muscle strength were evaluated in 35 patients and in 20 healthy subjects. Respiratory pressures and electromyography of scalene and sternocleidomastoid muscles were continuously recorded during incremental maximal cardiopulmonary exercise testing until symptom limitation. Dyspnoea was assessed at rest, every 2 min during exercise and at the end of exercise with a modified Borg scale.

Main results

Inspiratory muscle strength measurements were significantly lower for patients in comparison to controls (all p<0.05). Patients achieved lower peak of exercise (lower oxygen consumption) compared to controls, with both gastric (−9.8±4.6 cmH₂O versus 8.9±6.0 cmH₂O) and transdiaphragmatic (6.5±5.5 cmH₂O versus 26.9±10.9 cmH₂O) pressures significantly lower, along with larger activation of both scalene (40±22% EMGmax versus 18±14% EMGmax) and sternocleidomastoid (34±22% EMGmax versus 14±8% EMGmax). In addition, the paralysis group presented significant differences in breathing pattern during exercise (lower tidal volume and higher respiratory rate) with more dyspnoea symptoms compared to the control group.

Conclusion

The paralysis group presented with exercise limitation accompanied by impairment in transdiaphragmatic pressure generation and larger accessory inspiratory muscles activation compared to controls, thereby contributing to a neuromechanical dissociation and increased dyspnoea perception.

The exercise capacity limitation in patients with unilateral diaphragmatic paralysis is characterised by an inefficient hemidiaphragm contraction. Consequently, there is a neuromechanical dissociation with an overload of inspiratory accessory muscles and higher breathlessness.https://bit.ly/2XxAR4K

Diagnostic accuracy of the trans-abdominal ultrasound in the assessment of dysfunctional hemidiaphragm due to non-pulmonic etiology

Background

To evaluate the role of the trans-abdominal ultrasound (TAUS) in the assessment of hemidiaphragmatic dysfunction—due to non-pulmonic causes—as compared to the conventional CT; 36 patients (22 males and 14 females; age range 5 to 84 years) were included in this study.

Results

In CT examination, the dysfunctional hemidiaphragm was considered when either a hernia/post-traumatic defects (present in 19.4% of patients, of which 5.5% were depicted on the right side and 13.8% were existing on the left side), or elevated copulae (present in 80.6% of patients, of which 58.8% were found on the right side (21 patients) and 22.2% were seen on the left side (8 patients).

The TAUS showed a high sensitivity, specificity, PPV, NPV, and over all accuracy {100% (95% CI = 59.04 to 100.00%), 100% (95% CI = 88.06 to 100.00%), 100%, 100%, 100% (95% CI = 90.26 to 100.00%), respectively} in detection of defects and hernias as compared to CT. A high sensitivity, specificity, PPV, NPV, and over all accuracy {96.55% (95% CI = 82.24 to 99.9%), 100% (95% CI=59.04 to 100.00%), 100%, 87.5% (95% CI = 50.50 to 97.96%), 97.22% (95% CI = 85.47 to 99.93%), respectively} were found in detection of thickness and motion abnormalities, and in the detection of subphrenic collections in cases with relevant elevated copula in CT.

Conclusion

Trans-abdominal ultrasound (TAUS) could accurately assess the diaphragmatic thickness and provides a real-time image of a dysfunctional hemidiaphragm due to a diaphragmatic and infradiaphragmatic causes as well as the diaphragmatic defects with high sensitivity and specificity in comparison to CT.

Trans-diaphragmatic Pathologies: Anatomical Background and Spread of Disease on Cross-sectional Imaging

The diaphragm is not only a sheet of muscle separating the abdominal and thoracic cavities: it plays an essential role in ventilation and can act as a gateway for the spread of different disease processes between the abdominal and the thoracic cavity. Careful attention to the appearance of the diaphragm on various imaging modalities is essential to ensure the accurate diagnosis of diaphragmatic disorders, which may be secondary to functional or anatomical derangements.

Magnetic Resonance Imaging of the Diaphragm: From Normal to Pathologic Findings

The diaphragm is a musculotendinous structure that divides the chest from the abdomen. Its motility, unintentional or voluntary, is crucial for the physiologic respiratory function due to its contribution to lung volume expansion and contraction. Therefore, diaphragmatic dysfunction may cause a respiratory failure without any pathology of the lungs. Different imaging modalities can be employed for diaphragmatic evaluation. Among all, magnetic resonance imaging (MRI) has demonstrated to be the most accurate technique in providing a morphologic and functional assessment of the diaphragm as well as information about the adjacent structures. However, its diagnostic value is still underrated and its performance is often far from the daily clinical practice. Backward, physicians and radiologists should be aware of the undoubted advantages of MRI and confident about the normal or pathologic imaging features, to avoid misdiagnosis.

Ultrasonographic evaluation of the diaphragm thickness in patients with multiple sclerosis

BACKGROUND

Diaphragm weakness or dysfunction have been previously reported in multiple sclerosis (MS) patients. The aim of this study was to evaluate diaphragm thickness and thickenning ratio (TR) using ultrasound in MS patients.

METHODS

This prospective study comprised MS patients and a control group. Ultrasound examination was performed using a linear transducer (6-15 MHz). The diaphragm was seen as a hypoechoic structre between the peritoneum and pleura. End-expirium and end-inspirium measurements were obtained. Change levels and TR (%) were calculated. All participants were assessed using the Expanded Distability Status Scale (EDSS) and Fatigue Severity Scale (FSS).

RESULTS

Evaluation was made of 45 MS patients (11 males, 34 females) with a mean age of 37.36±9.0 years and 36 healthy subjects (3 males, 33 females) with a mean age of 35.19±9.3 years. The diaphragm thicknesses were similar at end-expirium (1.86±0.3 vs. 1.83±0.3 mm) and end-inspirium (3.14±0.6 vs. 3.46±0.6 mm). The change level with inspirium (0.90±0.6 vs. 1.31±0.7 mm) and TR (49.77±37.7 vs. 72.30±40.1%) were significantly higher in the control group compared to the values of MS patients. A weak and negative correlation was determined between EDSS and TR values (r=-0.293, p = 0.008), and no significant correlation was observed between the FSS values and diaphragm thickness (p>0.05 for all).

CONCLUSION

Although the diaphragm thickness of MS patients seems to be similar to those of healthy subjects, the change level and TR of MS patients seem to be lower. Furthermore, the change level and TR were found to be associated with EDSS.

Assessing the effects of inspiratory muscle training in a patient with unilateral diaphragm dysfunction

A 55-year-old man was referred to the outpatient pulmonary department of our hospital because of dyspnoea during exertion and when bending forward, which had been present for at least 6 months. He reported experiencing severe symptoms of breathlessness and many of his daily activities had to be adapted or interrupt due to symptoms (as documented by the Baseline Dyspnea Index (BDI)) (table 1). Recent infectious episodes or episodes of neck or shoulder pain were absent. His medical history included systemic arterial hypertension, obesity (body mass index (BMI) 36 kg·m⁻²), and obstructive sleep apnoea for which he was treated with night-time continuous positive airway pressure therapy (8 cmH₂O). He was a former smoker (18 pack-years) who quit smoking 15 years ago. 8 months ago, he underwent abdominal surgery (transabdominal epigastric hernia repair). The presence of cardiopulmonary disease and other aetiologies, such as neuromuscular disease, was excluded. Chest radiograph showed an elevated left hemidiaphragm and impaired left phrenic nerve conduction (i.e. increased latency and compound muscle action potential (CMAP) duration) after electrical stimulation (table 1) [1].

Patients with diaphragm dysfunction experience exertional dyspnoea. Respiratory muscle function assessments can identify breathing abnormalities and IMT might help to reduce symptoms (mostly via improvements in non-diaphragmatic muscles).http://bit.ly/2QdxNFP